D.E.Q. Tests Passed, and HOW!
 

Boy, it really has been a long time since I've posted to this Board!

Just ran the '91 420SEL (@145Kmiles) through the Oregon Department of Environmental Quality's latest battery of emission tests: time to renew the registration. What really surprized me were the results!

TEST a). HC ppm Max 220 b). CO(%) Max 1.00 c).CO+CO2 (%) Min 6.0

RESULT

@idle 0 0.00 15.2
659 rpm

@load
2,500 rpm 3 0.02 15.4

This totally blew me away, as it is often necessary to run older cars through three or four times (usually after multiple repair$) in order to get a pass. I do use premium gas exclusively.

The plugs are recently replaced non-platinum Bosch, the oil & filter was changed last week, the coolant has been changed to G-05, the air filter has about 5k on it... Other than this normal maintenance, the car is running on the plug wires, distributor cap and rotor from the previous owner's last dealership major service of 3/99, almost exactly 50K miles ago!

Is this typical of W126 cars? Should I leave "well enough alone" at the 150K point or go with a new distributor cap, rotor and plug wires?

Cheers!

p.s. I don't seem to be able to get the results to properly allign with the test parameters, for some reason: the readings at idle were 0 for HC, 0.00 for CO% and 15.2 for the CO+CO2%. At load (2,500rpm) they were 3 for HC, 0.02 for CO% and 15.4 for CO+CO2%

Should I leave "well enough alone" at the 150K point or go with a new distributor cap, rotor and plug wires?

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Always remember that old, but true, saying: "If it ain't broke, etc".....

Are you sure the sampling probe was inserted into the tailpipe?
I expect to see these kind of readings when the probe is just laying on the floor. ;)

These numbers are "unusually low"! Do you have any prior test history?

I encourage all to save emission test reports as they can show trends that can be useful in troubleshooting if the car ever fails or to flag "suspect" results that dont' jibe with test history.

Duke

That's really funny. I sort of thought the same thing myself.

Those numbers are great for the engine OFF.

What were they with the engine RUNNING? ;)

Interestingly enough...
 

...I actually still do have the DEQ test results from 2 years ago.

They have changed the format, in that the reported readings are from a test on a rear wheel roller, with the car in drive, vs. the idle/2,500 rpm readings from the current test.

The results are in grams/mile, with the THC (Total HydroCarbons?) allowable at 1.20 and the reading for the 420SEL at 0.04, NOx at 3.00, with the car at 0.73, CO at 30.0 with the car at 1.6 and a final test for CO2 with no standard stated but a reading of 833.9 for my car. In both cases the engine was definitely "on"... As to where they stuck the probe, I defer to their professional expertise...

I don't know how these test results, expressed as they are in grams/mile, compare with the recent ppm readings. I do note that the cost of plates & registration for two years went up by $24 to a total of $75, which includes the $21 DEQ testing. ;)

Cheers!